Signal processing apparatus and method of generating audio signal

ABSTRACT

A signal processing apparatus: specifies a capture time of a plurality of captured images that are captured from respectively different directions by a plurality of cameras in order to generate a virtual-viewpoint image corresponding to a designated virtual viewpoint; obtain an audio collection signal based on collection of audio of an audio collection target region by a microphone, wherein the audio collection target region includes at least a part of a capturing range of the plurality of cameras; generates an audio signal to be reproduced together with the virtual-viewpoint image corresponding to the capture time specified by the specification unit, by using the obtained audio collection signal based on collection by the microphone at a point in time prior to the specified capture time.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a signal processing apparatus and amethod for generating audio signal corresponding to image content.

Description of the Related Art

A technique in which a plurality of cameras are installed at differingpositions, synchronous capture is performed thereby at multipleviewpoints, and virtual-viewpoint content is generated by using themulti-view images obtained by the capturing is gaining attention. Byvirtue of this technique for generating virtual-viewpoint content frommulti-view images, because it is possible to view a highlight scene of asoccer or basketball game from various angles, it is possible to providemore of a sense of presence to a user than with normal images forexample. Also, causing sound volume to change in accordance with thefocus of the image in a case where images and audio are reproducedsimultaneously is known (patent document 1).

[Patent document 1] Japanese Patent Laid-Open No. 2016-025633

Virtual-viewpoint content may be still image virtual-viewpoint contentgenerated from images that a plurality of cameras captured at one timeand may be moving image virtual-viewpoint content generated from imagesthat a plurality of cameras captured in a fixed period. Both still imagevirtual-viewpoint content and moving image virtual-viewpoint content arehandled as multi-viewpoint moving images involving a switching ofvirtual viewpoints when viewing, and provide a user an enhanced sense ofpresence.

However, in conventional techniques, there are cases where it is notpossible to provide the user with a sense of presence for audio in thereproduction of the virtual-viewpoint content. For example, the stillimage virtual-viewpoint content is generated from images captured at onetime, and thus there is no audio corresponding to the reproductionperiod. As a result, it is silent during playback of the still imagevirtual-viewpoint content or the audio becomes out of sync with theimage after reproduction of the still image virtual-viewpoint content,and not only it is not possible to provide the user with a sense ofpresence, the user is left with a sense of unnaturalness.

SUMMARY OF THE INVENTION

By virtue of an embodiment of the present invention, a signal processingapparatus and a signal processing method by which it is possible toprovide audio content relating to image content at a virtual viewpointare disclosed.

According to one aspect of the present invention, there is provided asignal processing apparatus, comprising: a specification unit configuredto specify a capture time of a plurality of captured images that arecaptured from respectively different directions by a plurality ofcameras in order to generate a virtual-viewpoint image corresponding toa designated virtual viewpoint; an obtainment unit configured to obtainan audio collection signal based on collection of audio of an audiocollection target region by a microphone, wherein the audio collectiontarget region includes at least a part of a capturing range of theplurality of cameras; and a generation unit configured to generate anaudio signal to be reproduced together with the virtual-viewpoint imagecorresponding to the capture time specified by the specification unit,by using the audio collection signal based on collection by themicrophone at a point in time prior to the specified capture time, theaudio collection signal being obtained by the obtainment unit.

According to another aspect of the present invention, there is provideda method of generating an audio signal, comprising: specifying a capturetime of a plurality of captured images that are captured fromrespectively different directions by a plurality of cameras in order togenerate a virtual-viewpoint image corresponding to a designated virtualviewpoint; obtaining an audio collection signal based on collection ofaudio of an audio collection target region by a microphone, wherein theaudio collection target region includes at least a part of a capturingrange of the plurality of cameras; and generating an audio signal to bereproduced together with the virtual-viewpoint image corresponding tothe specified capture time, by using the obtained audio collectionsignal, wherein the audio collection signal is based on collection bythe microphone at a point in time prior to the specified capture time.

According to another aspect of the present invention, there is provideda non-transitory computer-readable storage medium storing a program forcausing a computer to execute a method of generating an audio signal,the method comprising: specifying a capture time of a plurality ofcaptured images that are captured from respectively different directionsby a plurality of cameras in order to generate a virtual-viewpoint imagecorresponding to a designated virtual viewpoint; obtaining an audiocollection signal based on collection of audio of an audio collectiontarget region by a microphone, wherein the audio collection targetregion includes at least a part of a capturing range of the plurality ofcameras; and generating an audio signal to be reproduced together withthe virtual-viewpoint image corresponding to the specified capture time,by using the obtained audio collection signal, wherein the audiocollection signal is based on collection by the microphone at a point intime prior to the specified capture time.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating an example of a deviceconfiguration of a video processing system according to a firstembodiment.

FIG. 1B is a block diagram illustrating an example of a hardwareconfiguration of an image/audio processing apparatus.

FIG. 2 is a flowchart illustrating image/audio processing according tothe first embodiment.

FIG. 3 is a flowchart illustrating processing for determining reuse ofaudio according to the first embodiment.

FIG. 4 is a view of a correlation between audio and images for each timeaccording to the first embodiment.

FIG. 5 is a view of an installation of cameras and microphones in astadium according to a second embodiment.

FIG. 6 is a view for describing an example of a data configuration ofaudio according to the second embodiment.

FIG. 7 is a flowchart illustrating processing for selecting audioaccording to the second embodiment.

FIG. 8 is a flowchart illustrating processing for selecting audio, fromwhich virtual surround sound is generated, according to a thirdembodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, referring to the attached drawings, embodiments of thepresent invention will be described in detail.

First Embodiment

In the first embodiment, description is given regarding an operation forperforming a determination of the time of the audio to be used and theprocessing to be executed in a case where audio content is generated. Inthe first embodiment, it is assumed that there are types of imagecontent that can be generated: still image virtual-viewpoint content,moving image virtual-viewpoint content, and live image content. The liveimage content is image content used in a live broadcast, and is imagecontent for which one selected camera image is used from among aplurality of cameras at each time. The moving image virtual-viewpointcontent is a moving image generated based on multi-viewpoint images (aplurality of captured images) captured by a plurality of cameras in apredetermined period from differing directions respectively, andcorresponding to an arbitrarily designated virtual viewpoint. The stillimage virtual-viewpoint content is a moving image generated based onmulti-viewpoint images captured by a plurality of cameras at a singlepoint in time from directions different to each other, and correspondsto a virtual viewpoint that changes in the period of the moving image.In the embodiment hereinafter, a single virtual-viewpoint image isrecited in a case where there is no distinction between moving imagevirtual-viewpoint content and still image virtual-viewpoint content.

Meanwhile, in the present embodiment, there exist two types of audiocontent that can be generated: virtual surround sound content and liveaudio content. The virtual surround sound content is audio content thatapplies pseudo-surround sound effect processing by using informationsuch as a position of an object in the image content or a position fromwhich a camera captures. The live audio content is audio content used ina live broadcast, and is 2ch audio content generated based on audio datacollected from two selected microphones, for example.

Device Configuration and Processing of Each Block

FIG. 1A is a block diagram illustrating an example of a deviceconfiguration of a video processing system according to a firstembodiment. A video processing system is equipped with an image/audioprocessing apparatus 100, a camera group 101, a microphone group 102, atime generation server 103, and a video delivery apparatus 104. Theimage/audio processing apparatus 100 receives a number of pieces ofimage data (captured images) according to the number of cameras from thecamera group 101 and a number of pieces of audio data (sound pickupsignal) according to the number of microphones from the microphone group102.

The camera group 101 is configured by a plurality of cameras forcapturing objects from a plurality of directions. The microphone group102 is configured by a plurality of microphones. In the presentembodiment, an audio collection target region in which the microphonegroup 102 performs audio collection includes at least a portion of acapturing range of the camera group 101. The time generation server 103generates time information, and sends it to the camera group 101 and themicrophone group 102. The cameras and microphones that configure thecamera group 101 and the microphone group 102 receive time informationfrom the time generation server 103, append the time information toimages and audio, and then send them to the image/audio processingapparatus 100. Note, configuration may be taken such that the timegeneration server 103 sends the time information to the image/audioprocessing apparatus 100, and the image/audio processing apparatus 100appends the time information to the images and the audio.

Next, description regarding the configuration of the image/audioprocessing apparatus 100 is given. An image input unit 110 accepts inputof the images that the camera group 101 captured to obtain the images,and transfers them to a storage unit 112. An audio input unit 111obtains audio (audio collection signal) that the microphone group 102collected, and transfers it to the storage unit 112. The storage unit112 stores the image data obtained from the image input unit 110 (theimage data obtained by the plurality of cameras of the camera group 101)and audio data that the audio input unit 111 obtained (the audio dataobtained by the plurality of microphones of the microphone group 102).The images and audio stored in the storage unit 112 are referred to asimage data 113 and audio data 114 respectively. A video generationcontrol unit 118 transfers instructions and setting values of a userrelating to generation of video content to an image control unit 115, asynchronization control unit 116, and an audio control unit 117. Note,in the present specification, video content is assumed to be contentincluding image content and audio content to be reproduced together withthe image content.

The image control unit 115 determines the type of the generated imagecontent based on the image data 113 in accordance with an instruction bythe video generation control unit 118. In a case where still imagevirtual content is generated, the image control unit 115 transfers imagedata 113 read from the storage unit 112 to a still imagevirtual-viewpoint content generation unit 119. In a case where movingimage virtual-viewpoint content is generated, the image control unit 115transfers image data 113 read from the storage unit 112 to a movingimage virtual-viewpoint content generation unit 120. In a case wherelive image content is generated, the image control unit 115 transfersimage data 113 read from the storage unit 112 to a live image contentgeneration unit 121. Also, the image control unit 115 transfers theabove described type of generated image content, time information of theread image data, and the like to the synchronization control unit 116.

The synchronization control unit 116 obtains the type of image content,a time stamp of the image data 113, a start time of image contentgeneration, object coordinates of the image data 113, and the like fromthe image control unit 115 or the video generation control unit 118, andtransfers these to the audio control unit 117. The audio control unit117, based on either or both of an instruction from the video generationcontrol unit 118 and a determination within the audio control unit 117based on information obtained from the synchronization control unit 116,determines the type of the audio content to be generated and the type ofthe audio data to be used. In a case where virtual surround soundcontent is generated, the audio control unit 117 transfers audio data114 read from the storage unit 112 to a virtual surround sound contentgeneration unit 122. In a case where live audio content is generated,the audio control unit 117 transfers audio data 114 read from thestorage unit 112 to a live audio content generation unit 123.

The still image virtual-viewpoint content generation unit 119 generatesstill image virtual-viewpoint content by using the image data 113obtained from the image control unit 115, and transfers it to amultiplexing unit 124. The moving image virtual-viewpoint contentgeneration unit 120 generates moving image virtual-viewpoint content byusing the image data 113 obtained from the image control unit 115, andtransfers it to the multiplexing unit 124. The live image contentgeneration unit 121 generates live image content by using the image data113 obtained from the image control unit 115, and transfers it to themultiplexing unit 124. The virtual surround sound content generationunit 122 generates virtual surround sound content by using the audiodata 114 obtained from the audio control unit 117, and transfers it tothe multiplexing unit 124. The live audio content generation unit 123generates live audio content by using the audio data 114 obtained fromthe audio control unit 117, and transfers it to the multiplexing unit124.

The multiplexing unit 124 and an image output unit 125 execute controlfor causing the audio content to be reproduced together with the imagecontent. The multiplexing unit 124 obtains image content from the stillimage virtual-viewpoint content generation unit 119, the moving imagevirtual-viewpoint content generation unit 120, and the live imagecontent generation unit 121. Also, the multiplexing unit 124 obtains theaudio content from the virtual surround sound content generation unit122 and the live audio content generation unit 123. Then, themultiplexing unit 124 multiplexes the image content and the audiocontent into one data sequence to generate video content, and outputsthe video content to the image output unit 125. The image output unit125 outputs the video content obtained from the multiplexing unit 124 tothe video delivery apparatus 104.

FIG. 1B is a view illustrating an example of the hardware configurationof the image/audio processing apparatus 100 according to the firstembodiment. A CPU 11 realizes the above described functional units byexecuting programs held in a ROM 12 which is a read-only memory or in areadable/writable RAM 13 as necessary. An interface 14 connects theimage/audio processing apparatus 100 to an external device such as thecamera group 101, the microphone group 102, or the video deliveryapparatus 104. An input unit 15 accepts various input by the user. Adisplay unit 16 is a liquid crystal display for example, and performsvarious display under the control of the CPU 11. A storage apparatus 17is configured by a hard disk drive, for example, and realizes thestorage unit 112. Also, the storage apparatus 17 stores variousprograms, and necessary programs are appropriately loaded to the RAM 13for execution by the CPU 11. The above described configurations areconnected via an internal bus 18 so as to be able to communicate witheach other.

Operation

Description is given regarding operation of the image/audio processingapparatus 100 equipped with the above configurations. FIG. 2 is aflowchart for describing image/audio processing according to the firstembodiment. In the present embodiment, audio content reproduced togetherwith image content is generated by using previous audio data which isaudio data collected at a time prior to the capturing time correspondingto image content of a virtual viewpoint generated based on image data.Note, in the present embodiment, image content for a virtual viewpointwith which audio content generated by using previous audio data isassociated is still image virtual-viewpoint content.

In step S20, the video generation control unit 118 sets a reuse modewith respect to the audio control unit 117. In the present embodiment,three types of reuse modes can be set: a user instruction mode, anautomatic-time-stamp-determination mode, and anautomatic-content-determination mode. Note, the reuse mode is designatedby the user via a predetermined user interface (the input unit 15).Configuration may be taken such that the reuse mode can be set again atany time. Specific operation of each mode is described later using FIG.3. Also, the mode is not necessarily limited to reused data because allof the audio data 114 is targeted. In other words, a case in which audiodata that was not used in the past is used is also possible.

In step S21, the video generation control unit 118 performs an imagecontent setting with respect to the image control unit 115. The type ofcontent to be generated, the time at which generation is to start, thetime at which generation is to end, setting values for the camera group101, and the like are included in the image content setting. Note, theimage content setting is also conveyed to the synchronization controlunit 116. In step S22, the video generation control unit 118 performs anaudio content setting with respect to the audio control unit 117. Thenumber of channels of the content to be generated, the setting values ofthe microphone group 102, and the like are included in the audio contentsetting.

In step S23, the video generation control unit 118 instructs a start ofimage capturing and audio collection to the camera group 101, themicrophone group 102, and the image/audio processing apparatus 100. Bythis instruction, storage of images that the image input unit 110receives from the camera group 101 to the storage unit 112 and storageof audio that the audio input unit 111 receives from the microphonegroup 102 to the storage unit 112 is started.

Step S211 to step 5215 are editing processes for generating videocontent including image content and audio content by using the imagedata 113 and the audio data 114 stored in the storage unit 112. When astart of video editing is instructed, the video generation control unit118 starts video editing processing (step S211, YES). The video editingprocessing includes generation of image content by the image controlunit 115 (step S212), generation of audio content by the audio controlunit 117 (step S213), and generation of video content by themultiplexing unit 124 (step S214). In the generation of the imagecontent, the image control unit 115 reads, from the storage unit 112,image data to be used in the generation of the image content, andtransfers the image data to one of the content generation units 119 to121 in accordance with the type of the image content that the userdesignated. In the generation of the audio content, the audio controlunit 117 reads, from the storage unit 112, the audio data specifiedbased on a time stamp of the image data used in the generation of theimage content, and transfers it to one of the content generation units122 to 123. In the generation of the video content, the multiplexingunit 124 multiplexes into a single data sequence and outputs the imagecontent and the audio content accepted from respective contentgeneration units. The user can immediately view/listen to the videocontent as an editing result. Until there is an instruction to end theediting by the user, the processing of step S212 to step S214 repeats(step S215).

For example, in FIG. 4, the user generates image content by reproducingimage data from a time stamp tn0. Meanwhile, the image data istransferred to the live image content generation unit 121, and liveimage content is generated thereby. When an image of time stamp tn1(time T1) is reproduced, a user performs a pause, a still image isdisplayed, and then the viewpoint is caused to move. Meanwhile,necessary image data is transferred to the still image virtual-viewpointcontent generation unit 119, and still image virtual-viewpoint contentis generated thereby. After this, when the moving image reproduction(the time T2) is resumed, images from the time stamp tn1 onwards arereproduced and live image content is generated. When the video editingis ended when the image of the time stamp tn2 is reproduced (time T3),image content of a configuration as illustrated in FIG. 4 is generated.Specifically, the image content illustrated in FIG. 4 includes a periodin which a virtual-viewpoint image is reproduced and a period in which acaptured image that is captured by a camera is reproduced.

In the generation of the audio content reproduced together with theimage content as described above, the audio control unit 117 normallyselects audio used in the generation of the audio content based on timestamps of the images. For example, the audio control unit 117 generateslive audio content 40 and 41 as audio data corresponding to live imagecontent 44 (FIG. 4). At that time, the audio control unit 117 generatesaudio content by sending audio data corresponding to the image data usedin the generation of the live image content 44 to the live audio contentgeneration unit 123. In a case of the still image virtual-viewpointcontent, audio for generating audio content is not obtained becausethere is only one time stamp. Accordingly, the audio control unit 117generates audio content for the still image virtual content by sending areuse instruction to the virtual surround sound content generation unit122.

Step S24 to step S26 are processes by which the audio control unit 117outputs such a reuse instruction to the virtual surround sound contentgeneration unit 122. The processing of step S24 to step S26 can beexecuted substantially in parallel with the processing of step S211 tostep S215. In step S24, the audio control unit 117 determines whether ornot to reuse audio data in accordance with the reuse mode setting thatthe video generation control unit 118 set in step S20. Descriptionregarding the details of step S24 is given later with reference to theflowchart of FIG. 3. In a case where it is determined that audio datawill be reused, the audio control unit 117, in step S25, specifies animage content start time and a reproduction period for the image contentnecessary for reuse by obtaining them from the synchronization controlunit 116. Then, in step S26, the audio control unit 117 transfers theaudio data, the start time of the image content, and the reproductionperiod of the image content to the virtual surround sound contentgeneration unit 122. In this step, the audio control unit 117 may conveyto the video generation control unit 118 that the instruction completed.In a case where it is determined in step S24 that audio data will not bereused, the above described step S25 and step S26 are skipped. Also,because audio data reuse is executed during the reproduction periodobtained in step S25, the processing enters a standby state over thisreproduction period in step S26, and the processing returns to step S24when the reproduction period has elapsed.

In step S27, the video generation control unit 118 confirms aninstruction of the user in order to determine whether to continue imagecapturing and audio collection. In a case where the image capturing andaudio collection is to be continued, the processing returns to step S24,and in a case where the image capturing and audio collection is not tobe continued, the processing advances to step S28. In step S28, thevideo generation control unit 118 performs processing to end imagecapturing and audio collection.

Next, description regarding the reuse determination executed in step S24is given using FIG. 3. The flowchart of FIG. 3 illustrates the detailsof step S24.

In step S30, the audio control unit 117 confirms what reuse mode thathas been set. The reuse mode may be a user instruction mode fordetermining execution of the above described reuse in accordance with auser instruction or an automatic determination mode for automaticallydetermining execution of the above described reuse based on the imagecontent. The automatic determination mode may be anautomatic-content-determination mode in which the audio control unit 117executes the reuse determination based on the type of image content thatis generated or an automatic-time-stamp-determination mode in which theaudio control unit 117 executes the reuse determination based on timestamp information of the image content. In the case of the userinstruction mode, the processing advances to step S31. In the case ofthe automatic-content-determination mode, the processing advances tostep S32. In the case of the automatic-time-stamp-determination mode,the processing advances to step S33.

In the user instruction mode, it is determined whether or not to executea reuse of audio data in accordance with an instruction from the user.In step S31, the audio control unit 117 confirms whether or not there isa reuse instruction from the user by obtaining information from thesynchronization control unit 116. In a case where there is a reuseinstruction from the user, the processing advances in step S36, and in acase where there is no reuse instruction from the user, the processingadvances to step S35.

In the automatic-content-determination mode, in a case where it isdetermined that the image content is a still image from a virtualviewpoint, in other words, in a case where it is determined that theimage content is still image virtual-viewpoint content, it is determinedthat a reuse of the audio data will be executed. In step S32, the audiocontrol unit 117 confirms the type of image content being generated byobtaining information from the synchronization control unit 116. In acase where the image content is still image virtual-viewpoint content,the processing advances to step S36, and in a case where the imagecontent is moving image virtual-viewpoint content or live image content,the processing advances to step S35.

In the automatic-time-stamp-determination mode, it is determined whetheror not to execute a reuse of the audio data based on a reproduction timeand time stamp of the image data being used in the generation of theimage content. In step S33, the audio control unit 117 compares the timestamp of the image data 113 to be used to generate the image contentwith the reproduction time obtained from the video generation controlunit 118. In the case where they do not match, the processing advancesto step S36, and the audio control unit 117 determines to reuse theaudio data 114. In a case where the compared results match, theprocessing advances to step S34. Note, the time stamp and thereproduction time generally are not the same values. For example, inFIG. 4, time T0≠time stamp tn0 and time T1≠the time stamp tn1. In thepresent embodiment, in a case where the difference between the capturingtime of the image data corresponding to the image content and thereproduction time of the image content changed, it is determined that areuse will be performed. For example, the difference between the time T0and the time stamp tn0 is set as a reference. At the time T1+ΔT, thetime stamp of the image data used in the still image virtual-viewpointcontent is still tn1, and so the difference between the capturing timeof the image data and the reproduction time of the image contentchanges. In step S33, the change is detected. Also, in a case wheremonitoring for a change in the difference is resumed in accordance withthe end of the standby state (reproduction period elapses) in step S26,the difference between the current reproduction time and the time stampis set as a reference.

In step S34, the audio control unit 117 obtains the time stamp of theimage data 113 to be used to generate the image content from thesynchronization control unit 116. Then, it determines whether the timeis continuous by comparing it with the time stamp of the image data usedin the generation of the image content of the previous reproductiontime. In the case where the times are continuous, the processingadvances to step S35, and the audio control unit 117 determines to notreuse the audio data 114. In the case where the times are discontinuous,the processing advances to step S36, and the audio control unit 117determines to reuse the audio data 114.

Example of Processing Result

Next, using FIG. 4, a transition of data in a case of determining thatthe audio data 114 will be reused, and viewing/listening to virtualsurround sound content while browsing still image virtual-viewpointcontent will be described. FIG. 4 illustrates a case where audio contentand image content are reproduced between the time T0 and the time T3.

From the time T0 to the time T1, the live image content generation unit121 generates the live image content 44, and the live audio contentgeneration unit 123 generates the live audio content 40 and the liveaudio content 41. These contents are multiplexed in the multiplexingunit 124, and the result is outputted from the image output unit 125 asvideo content. The time stamps of the image data used to create the liveimage content 44 are tn0 to tn1. Between T0 and T1, the differencebetween the time stamp and the reproduction time of the image data usedfor generating live image content remains as the difference between thetime of playback initiation and the time stamp (Δt=T0−tn0). For thisreason, in the automatic-time-stamp-determination mode, it is determinedthat the audio data will not be reused. Also, the synchronizationcontrol unit 116 makes a notification to the audio control unit 117 thatlive image content is to be generated. Accordingly, in a case of theautomatic-content-determination mode, the audio control unit 117determines that the audio data will not be reused based on thisnotification.

From the time T1 to the time T2, the still image virtual-viewpointcontent generation unit 119 generates still image virtual-viewpointcontent 45 and outputs it from the image output unit 125. For example,when the user makes an instruction for a generation of still imagevirtual-viewpoint content by a predetermined operation at the time T1, anotification of this instruction is made to the image control unit 115from the video generation control unit 118. The image control unit 115,after receiving this instruction notification, causes the generation ofthe still image virtual-viewpoint content by the still imagevirtual-viewpoint content generation unit 119 to start, and causes thegeneration of the live image by the live image content generation unit121 to stop. Also, the generation of the audio content is stopped in thelive audio content generation unit 123 because there ceases to be audiodata used for the generation of the audio content in conjunction withthe stoppage of generation of live images.

The audio control unit 117 repeatedly determines whether or not to reuseaudio data (step S24). In a case where the reuse mode is for automaticcontent determination, it is detected that the type of content to begenerated became still image virtual-viewpoint content at the time T1,and it is determined that audio data will be reused (step S32 (YES)→stepS36). The detection that the content became still imagevirtual-viewpoint content is made by the audio control unit 117receiving a notification of the content type from the synchronizationcontrol unit 116, for example. Alternatively, configuration may be takensuch that the audio control unit 117 determines the content type frommetadata of content (image data) that the still image virtual-viewpointcontent generation unit 119 outputs. Also, progress of the time stamp ofthe image data that is used for still image virtual-viewpoint content isstopped, and since it becomes discontinuous (in FIG. 4, it remains astn1), the difference between the reproduction time and the time stamp ofthe image data ceases to remain as the above-described Δt. In a casewhere the reuse mode is for automatic time stamp determination, it isdetermined that audio data will be reused upon detection of thesesituations (that Δt changes (step S33) or that time stamp stopsadvancing (becomes discontinuous) (step S34)).

In a case where it is determined that the audio data will be reused, theaudio control unit 117 conveys the start time T1 and the reproductionperiod (ΔT=T2−T1) together with making an instruction for a start of thegeneration of the virtual surround sound content to the virtual surroundsound content generation unit 122. Also, the audio control unit 117reads audio data (audio data for which the time stamp is between tn1−ΔTand tn1) corresponding to reproduction times between T1−ΔT=2T1−T2 and T1from the storage unit 112, and transfers the result to the virtualsurround sound content generation unit 122. The virtual surround soundcontent generation unit 122, by using the audio data corresponding tothe time 2T1−T2 to the time T1, generates audio content (virtualsurround sound content) for listening between the time T1 and the timeT2 and outputs this to the image output unit 125. Note that in thepresent embodiment, audio data is selected in order to generate virtualsurround sound content based on the virtual-viewpoint position of thestill image virtual-viewpoint content. For example, the audio datacollected from microphones close to the cameras (viewpoint) providingthe image data used at the time when generation of still imagevirtual-viewpoint content is started (time T1) is used in the generationof the virtual surround sound content. Of course, the selection of theaudio data to be used is not limited to this. For example, configurationmay be taken to use audio data that was used in the generation of audiocontent when the reproduction time is between 2T1−T2 and T1.

When insertion of the still image virtual-viewpoint content is ended(when time T2 is reached), the image control unit 115 causes thegeneration of content by the still image virtual-viewpoint contentgeneration unit 119 to stop, and causes the generation of live imagecontent by the live image content generation unit 121 to resume. In theexample of FIG. 4, the generation of the live image content that wasinterrupted at time T1 when the generation of the still imagevirtual-viewpoint content was started is resumed. Specifically, the liveimage content is generated by using image data from time stamp tn1.However, in a case where the viewpoint moved in the still imagevirtual-viewpoint content, the image data from a camera close to thefinal position of the viewpoint is used. By doing this, continuity ofthe images is maintained resulting in a natural reproduced image.

From the time T2 to the time T3, the live image content generation unit121 generates live image content 46 and outputs it to the multiplexingunit 124. Also, together with this, the live audio content generationunit 123 generates live audio content 43 and outputs it to themultiplexing unit 124. The multiplexing unit 124 multiplexes the liveimage content 46 and the live audio content 43 into one data sequence togenerate video content, and outputs the video content to the imageoutput unit 125. As described above, at a timing (T2) at which theperiod in which the still image virtual-viewpoint content is reproducedends, audio content generated by using a sound pickup signal ofapproximately the same time as the capturing time corresponding to theimage content of that timing is reproduced. Specifically, it is possibleto listen to continuous audio when switching from the still imagevirtual-viewpoint content to other content (the live image content inFIG. 4). For this reason, the user can listen to realistic audio withouta sense of unnaturalness.

Note, while the generation of still image virtual-viewpoint content isstarted at the time T1 (arbitrary time) in the present embodiment, it isassumed that ΔT which is the reproduction period is set in advance. Theembodiment is not limited to this. For example, configuration may betaken such that the reproduction period can be designated together withan instruction to generate still image virtual-viewpoint content. Forexample, configuration may be taken such that a button for generatingfive seconds of still image virtual-viewpoint content, a button forgenerating ten seconds of still image virtual-viewpoint content, and thelike are provided, and the reproduction period ΔT is determined bymaking an instruction in relation to one of the buttons. Alternatively,in a configuration in which it is possible to cause the still imagevirtual viewpoint direction to rotate 360 degrees with respect to anobject, configuration may be taken such that the time necessary torotate 360 degrees is set in advance and the reproduction period is setin accordance with the designated amount of rotation. In such a case,when an instruction is made to cause the virtual-viewpoint direction torotate 180 degrees with respect to an object together with thegeneration of still image virtual-viewpoint content for example, half ofthe time required for a rotation of 360 degrees is set as thereproduction period of the still image virtual-viewpoint content.

Also, although audio data of a period of ΔT immediately preceding stillimage virtual-viewpoint content is used in the reuse of the audio datain the above described embodiment, limitation is not made to this.Configuration may be taken such that audio data of an arbitrary timingprior to a time stamp of the still image virtual-viewpoint content isused from among the audio data 114 stored in the storage unit 112together with the image data 113. Specifically, configuration may betaken such that reproduced audio content is generated together withstill image virtual-viewpoint content by using the audio data collectedat a time before a capturing time corresponding to the still imagevirtual-viewpoint content. However, it is advantageous that audio dataof the time 2T1−T2 to the time T1 is used in a case where image contentis generated as in FIG. 4. This is because good audio continuity at thetime T2 can be achieved thereby.

As described above, by virtue of the first embodiment, a capturing timeof image data used for a generation of image content is specified, andaudio content is generated for reproduction together with correspondingimage content by using audio data based on collection by microphones ata time prior to the capturing time. Accordingly, even in a case whereaudio data corresponding to images is not present as with still imagevirtual-viewpoint content, the user can listen to audio. Also, the audiodata used for the generation of this audio is audio data related to theimage data used for the generation of the video content, and the usercan continue to listen without a sense of unnaturalness. In particular,as illustrated in FIG. 4, the continuity of the audio can be improved byusing audio data corresponding to a period of the times 2T2−T1 to T1 togenerate audio content corresponding to time T1 to T2 which is thereproduction period of the still image virtual-viewpoint content.

Note, although description is given centering on a case where stillimage virtual-viewpoint content is inserted into image content in thepresent embodiment, limitation is not made to this. For example, it ispossible to apply the above described embodiment even in a case whereslow motion moving image virtual-viewpoint content is inserted.Specifically, configuration may be taken such that an audio signal to bereproduced together with moving image virtual-viewpoint content isgenerated by using an audio collection signal based on audio collectionat a time before the capturing time of images used to generate themoving image virtual-viewpoint content. Even in such a case, a sense ofunnaturalness in viewing/listening by the user can be reduced similarlyto in the above described embodiment.

Second Embodiment

In the first embodiment, description was given of a configuration inwhich audio data from microphones close to a viewpoint corresponding towhen a generation of still image virtual-viewpoint content is started isused to generate audio content when generating the still imagevirtual-viewpoint content. However, the method of selecting the audiodata when generating still image virtual-viewpoint content is notlimited to this. In the second embodiment, description regarding aconfiguration in which audio data is selected based on the position ofan object in a case where virtual surround sound content correspondingto still image virtual-viewpoint content is generated. Note, theconfigurations of the video processing system and the image/audioprocessing apparatus 100 are the same as in the first embodiment (FIG.1A and FIG. 1B).

Example of Installation of Cameras and Microphones in a Stadium

FIG. 5 is an example of an installation of cameras and microphones in astadium. A stadium 500 has stands 501, a field 502, and a live room 503.Also, dividing the field 502 into four regions using the dashed lines, afirst quadrant is referred to as a divided area 560, a second quadrantis referred to as a divided area 561, a third quadrant is referred to asa divided area 562, and a fourth quadrant is referred to as a dividedarea 563. Microphones 510 to 517 are microphones installed within thefield 502. In the example of FIG. 5, two microphones are installed ineach of the divided areas 560 to 563. Microphones 520 to 523 aremicrophones installed within the stands 501. A microphone 530 is amicrophone installed in the live room 503. The microphones 510 to 517and 520 to 523 configure the microphone group 102. Cameras 540 to 557are cameras installed in the stands 501. The cameras 540 to 557configure the camera group 101.

Configuration of Audio Data

FIG. 6 is a view illustrating an internal structure of the audio data114 stored in the storage unit 112. The audio data 114 includes aplurality of categories: field audio 60 that the microphones 510 to 517collect; stand audio 61 that the microphones 520 to 523 collect; andlive audio 62 that the microphone 530 collects. The field audio 60 isaudio data collected in the field of the stadium. The stand audio 61 isaudio data collected in the stands of the stadium. The live audio 62 isaudio data obtained by collecting the audio of a live commentator. Theaudio control unit 117 selects necessary audio (at least one of thefield audio 60, the stand audio 61, and the live audio 62 in the presentexample) from the audio data 114 based on the time stamp or theviewpoint of the moving image content, and reads it from the storageunit 112. The audio control unit 117 determines a transmissiondestination of the read audio data in accordance with the type of movingimage content being generated from among the virtual surround soundcontent generation unit 122 and the live audio content generation unit123. The audio control unit 117 sends the read audio data to adetermined content generation unit.

Operation

Description regarding processing in which the audio control unit 117selects audio data used for the generation of audio content for stillimage virtual-viewpoint content from the audio data 114 is given usingthe flowchart of FIG. 7. The processing illustrated by the flowchart ofFIG. 7 is one example of the details of the processing of step S25 andstep S26 of FIG. 2.

In step S71, the audio control unit 117 obtains from the synchronizationcontrol unit 116 time stamp range information based on a time stamp ofimage data used to generate still image virtual-viewpoint content and areproduction period (ΔT of FIG. 4 for example) of the still imagevirtual-viewpoint content. The time stamp range information is a rangeof time stamps for obtaining audio data, and is a range of time stamps(tn1−ΔT to tn1) corresponding to the range of “2T1−T2” to “T1” of FIG. 4for example. In step S72, the audio control unit 117 obtains from thesynchronization control unit 116 area information in which an imagecontent object is present. The area information may be two-dimensionalor three-dimensional coordinates.

In step S73, the audio control unit 117 determines the audio data to betransferred to the virtual surround sound content generation unit 122based on the time stamp range information obtained in step S71 and thearea information obtained in step S72. For example, audio data of therange indicated in the time stamp range information obtained in step S71is determined as the audio data to be transferred from among the audiodata obtained from the microphones specified based on the areainformation obtained in step S72. In step S74, the audio control unit117 obtains the audio data determined in step S73 from among the audiodata 114. For example, audio data having time stamps of a rangeindicated by the time stamp range information obtained in step S71 andcollected from the microphones corresponding to the area that the areainformation obtained in step S72 indicates is obtained. In step S75, theaudio control unit 117 transfers the audio data obtained in step S74 tothe virtual surround sound content generation unit 122.

Concrete Example of the Selection of Audio Data

Hereinafter, an example of processing for selecting audio data by theaudio control unit 117 (step S73) is illustrated by using the example ofinstallation in the stadium 500 illustrated in FIG. 5 and the example ofthe configuration of the audio data 114 illustrated in FIG. 6. It isassumed that the generated image content is still imagevirtual-viewpoint content, and an object is present in the divided area561. In the case of still image virtual-viewpoint content, virtualsurround sound is generated because there is no corresponding audiodata.

For example, the following two types of methods of selecting audio dataare given. The first is a method for selecting only the stand audio 61,and the second is a method for selecting only the field audio 60. In themethod for selecting only the stand audio 61, audio data whose timestamps are in the range indicated by time stamp range information isselected from among audio data obtained from the microphone 521corresponding to the divided area 561 in which the object is present. Inthe method for selecting only the field audio 60, audio data whose timestamps are in the range indicated by time stamp range information isselected from among audio data obtained from the microphones 511 and 512(but not the microphone 521) which present in the divided area 561. Itis assumed that it is determined which selection method is to beemployed by a user setting.

Of course, the method of selecting the audio data is not limited to theabove. For example, configuration may be taken such that audio contentis generated by excluding audio data collected by a microphone at theclosest position from the position of the object of the image data usedfor the generation of image content (still image virtual-viewpointcontent). Note, live audio is not made to be the selection target in thepresent embodiment because discontinuity is noticeable when previousaudio data is reused.

As described above, by virtue of the second embodiment, it is possibleto select, by a user designation, a method of selecting audio data in acase of generating virtual surround sound for still imagevirtual-viewpoint content. For this reason, the user can listen tovarious audio and can experience a sense of presence in various wayswhen browsing still image virtual-viewpoint content.

Third Embodiment

In the first embodiment, a configuration in which audio data is selectedto generate audio content based on the position of a virtual viewpointis described, and in the second embodiment, a configuration in whichaudio data is selected to generate audio content based on the positionof an object of still image virtual-viewpoint content is described. Inthe third embodiment, a configuration in which audio content isgenerated based on a virtual viewpoint of still image virtual-viewpointcontent similarly to in the first embodiment is described. However, inthe third embodiment, a configuration in which it is possible to switchamong a plurality of methods of generating audio content using theposition of a virtual viewpoint is described. In particular, descriptionregarding a case where a method for generating virtual surround soundcontent so that audio in accordance with movement of the virtualviewpoint moves (a rotation for example) is included as one of thegeneration methods. Note, audio moving means that a virtual audiocollection position changes. Note, the configurations of the videoprocessing system and the image/audio processing apparatus 100 are thesame as in the first embodiment (FIG. 1A and FIG. 1B).

Types of Virtual Surround Sound

In the present embodiment, a configuration in which there are threetypes of methods for generating virtual surround sound is described. Thefirst generation method, which is a generation method according to acapture coordinate reference, moves the position of audio collection ofaudio content (rotated) based on movement of the position (hereinafterreferred to as capture coordinates) of a camera that captures an object,specifically the virtual viewpoint. In the generation method accordingto a capture coordinate reference, it is necessary to obtain a pluralityof capture coordinates. The second generation method, which is ageneration method according to an end reference, generates audio contentbased on a final capture coordinate of the still image virtual-viewpointcontent. The third generation method, which is a generation methodaccording to a start reference, generates audio content based on aninitial capture coordinate of the still image virtual-viewpoint content.

Note, in the generation method according to a capture coordinatereference, it is necessary to obtain capture coordinates together withmovement of the position of the virtual viewpoint. Also, in thegeneration method according to the end reference, virtual surround soundcontent is generated after the final capture coordinates of the stillimage virtual-viewpoint content are obtained. However, a case in whichthe movement path of the virtual viewpoint in the generation of thestill image virtual-viewpoint content is known in advance, in otherwords, a plurality of necessary capture coordinates or the final capturecoordinates are known in advance, it is possible to immediately obtainthe plurality of capture coordinates or the final capture coordinates.

Operation

FIG. 8, according to the third embodiment, is a flowchart illustratingprocessing for selecting, from among the audio data 114 stored in thestorage unit 112, audio data necessary for generating virtual surroundsound for still image virtual-viewpoint content.

In step S80, the audio control unit 117 obtains the virtual surroundsound generation method designated by the user from the synchronizationcontrol unit 116 or the video generation control unit 118. In a casewhere the designated generation method is the generation methodaccording to capture coordinate reference, the processing advances tostep S81, in a case where it is the generation method according to endcoordinate reference, the processing advances to step S83, and in a casewhere it is the generation method according to start coordinatereference, the processing advances to step S82. In step S81, the audiocontrol unit 117 obtains the plurality of capture coordinates of thecamera from the synchronization control unit 116. In step S82, the audiocontrol unit 117 obtains the capture coordinate for when the still imagevirtual-viewpoint content starts from the synchronization control unit116. In step S83, the audio control unit 117 obtains the capturecoordinate for when the virtual-viewpoint content ends from thesynchronization control unit 116.

After step S81-step S83, the processing advances to step S84. In stepS84, the audio control unit 117 selects a divided area based on thecapture coordinates obtained in step S81, step S82, or step S83. Forexample, the divided area in which the capture coordinates are presentis selected from among the divided areas 560 to 563 illustrated in FIG.5. A divided area in which a microphone necessary for generation ofvirtual surround sound is present is determined. In place of selecting adivided area, a configuration in which a microphone is selected may beemployed.

In step S85, the audio control unit 117 determines a microphone from thedivided area selected in step S84, and determines the audio data to beused. The processing of step S74 and step S75 is as described in FIG. 7.In the case of the generation method according to capture coordinatereference, a plurality of pieces of audio data corresponding to theplurality of capture coordinates are transmitted to the virtual surroundsound content generation unit 122, and the virtual surround soundcontent generation unit 122 generates audio content that moves inaccordance with the movement of the virtual viewpoint. In a case of thegeneration method according to start reference, audio data correspondingto a start coordinate is transferred to the virtual surround soundcontent generation unit 122, and the virtual surround sound contentgeneration unit 122 processes the audio data and generates audiocontent. For example, processing is performed such that sound is muffledas time elapses. In a case of the generation method according to endreference, audio data corresponding to an end coordinate is transferredto the virtual surround sound content generation unit 122, and thevirtual surround sound content generation unit 122 processes the audiodata and generates audio content. For example, conversely to the case ofthe generation method according to start reference, processing isperformed so as to the transition from a muffled sound to a sharp soundas time elapses.

As described above, in the present embodiment, it is possible todetermine input audio for generating virtual surround sound inaccordance with virtual-viewpoint content, and provide the user with animproved sense of presence by rotating the audio similarly to thevirtual viewpoint. Also, by providing a plurality of referencecoordinates, it is possible to leave room for the user to select among avariety of senses of presence.

Note, although a configuration in which generation of image content andgeneration of audio content is performed substantially in parallel isdescribed in each of the foregoing embodiments, limitation is not madeto this. Even in the case of processing for generating audio contentthat is attached later in relation to image content generated inadvance, such as in a situation in which the image content of T1 to T3in FIG. 4 is generated in advance, for example, it is possible to applythe above-described audio content generation. Also, in a case where thereuse mode is a user instruction mode, reuse of audio content isexecuted irrespective of the type of image content. For example, in acase where there was a reuse instruction from the user during thegeneration of live image content, audio content using previous audiodata over a period (reproduction period) determined beforehand isgenerated immediately after this instruction is performed.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-233499, filed Nov. 30, 2016 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A signal processing apparatus, comprising: aspecification unit configured to specify a capture time of a pluralityof captured images that are captured from respectively differentdirections by a plurality of cameras in order to generate avirtual-viewpoint image corresponding to a designated virtual viewpoint;an obtainment unit configured to obtain an audio collection signal basedon collection of audio of an audio collection target region by amicrophone, wherein the audio collection target region includes at leasta part of a capturing range of the plurality of cameras; and ageneration unit configured to generate an audio signal to be reproducedtogether with the virtual-viewpoint image corresponding to the capturetime specified by the specification unit, by using the audio collectionsignal based on collection by the microphone at a point in time prior tothe specified capture time, the audio collection signal being obtainedby the obtainment unit.
 2. The apparatus according to claim 1,comprising a control unit configured to execute control to cause theaudio signal generated by the generation unit to be reproduced togetherwith the virtual-viewpoint image.
 3. The apparatus according to claim 1,wherein the generation unit determines an audio collection signal to beused to generate the audio signal based on the capture time specified bythe specification unit and a reproduction period of thevirtual-viewpoint image.
 4. The apparatus according to claim 1, whereinthe generation unit generates the audio signal which is reproducedtogether with image content including a period in which thevirtual-viewpoint image is reproduced and a period in which a capturedimage captured by a camera is reproduced.
 5. The apparatus according toclaim 4, wherein the virtual-viewpoint image is a moving image generatedusing a plurality of captured images captured by the plurality ofcameras at a single capture time, and is a moving image corresponding toa virtual viewpoint that changes over a period of the moving image. 6.The apparatus according to claim 4, wherein the specification unitspecifies the capture time corresponding to the virtual-viewpoint imagebased on a time stamp of the image content.
 7. The apparatus accordingto claim 5, wherein the generation unit, in a case where the periodcorresponding to the virtual-viewpoint image in the image content isfrom T1 to T2, generates the audio signal which is to be reproduced inthe period from T1 to T2 by using an audio collection signal that is thesame as the audio collection signal to be used to generate the audiosignal to be reproduced in the period from 2T1-T2 to T1.
 8. Theapparatus according to claim 1, comprising an acceptance unit configuredto accept input of image content, wherein the generation unit, in a casewhere image content accepted by the acceptance unit includes avirtual-viewpoint image which is a moving image corresponding to asingle capture time, generates the audio signal using an audiocollection signal based on collection by the microphone at a point intime prior to the single capture time specified by the specificationunit.
 9. The apparatus according to claim 4, comprising an acceptanceunit configured to accept input of image content, wherein the generationunit, in a case where a capture time corresponding to a captured imageincluded in the image content accepted by the acceptance unit and acapture time corresponding to a virtual-viewpoint image included in theimage content are discontinuous, generates the audio signal by using anaudio collection signal based on collection by the microphone at a pointin time prior to the capture time corresponding to the virtual-viewpointimage specified by the specification unit.
 10. The apparatus accordingto claim 1, comprising an acceptance unit configured to accept input ofimage content, wherein the generation unit, in a case where a differencebetween a reproduction time of image content accepted by the acceptanceunit and a capture time of a captured image to be used for generation ofthe image content changes within a period of the image content,generates the audio signal using an audio collection signal based oncollection by the microphone at a point in time prior to the capturetime specified by the specification unit.
 11. The apparatus according toclaim 5, wherein the generation unit generates the audio signal to bereproduced together with the image content such that, at a timing atwhich the period over which the virtual-viewpoint image in the imagecontent is reproduced ends, an audio signal generated by using an audiocollection signal based on collection by the microphone at a point intime that is substantially the same as a capture time corresponding tothe image content of the timing is reproduced.
 12. The apparatusaccording to claim 1, wherein the virtual-viewpoint image is a slowmotion moving image.
 13. The apparatus according to claim 1, wherein thegeneration unit generates the audio signal to be reproduced togetherwith the virtual-viewpoint image by using an audio collection signalbased on collection by a microphone determined based on a position of avirtual viewpoint corresponding to the virtual-viewpoint image.
 14. Theapparatus according to claim 1, wherein the generation unit generates anaudio signal to be reproduced together with the virtual-viewpoint imageby using an audio collection signal based on collection by a microphonedetermined based on a position of an object included in the plurality ofcaptured images.
 15. The apparatus according to claim 1, wherein theaudio collection signal obtained by the obtainment unit includes fieldaudio in which audio of a field of a stadium is collected, and standaudio in which audio of stands of the stadium is collected, and thegeneration unit generates the audio signal by using the stand audiobased on collection at a point in time prior to the specified capturetime.
 16. The apparatus according to claim 13, wherein the generationunit generates the audio signal corresponding to a collection positionthat changes in accordance with movement of a virtual viewpoint in thevirtual-viewpoint image.
 17. The apparatus according to claim 13,wherein the generation unit generates the audio signal according to aposition of a virtual viewpoint when the virtual-viewpoint image isstarted.
 18. The apparatus according to claim 13, wherein the generationunit generates the audio signal according to a position of a virtualviewpoint when the virtual-viewpoint image ends.
 19. A method ofgenerating an audio signal, comprising: specifying a capture time of aplurality of captured images that are captured from respectivelydifferent directions by a plurality of cameras in order to generate avirtual-viewpoint image corresponding to a designated virtual viewpoint;obtaining an audio collection signal based on collection of audio of anaudio collection target region by a microphone, wherein the audiocollection target region includes at least a part of a capturing rangeof the plurality of cameras; and generating an audio signal to bereproduced together with the virtual-viewpoint image corresponding tothe specified capture time, by using the obtained audio collectionsignal, wherein the audio collection signal is based on collection bythe microphone at a point in time prior to the specified capture time.20. A non-transitory computer-readable storage medium storing a programfor causing a computer to execute a method of generating an audiosignal, the method comprising: specifying a capture time of a pluralityof captured images that are captured from respectively differentdirections by a plurality of cameras in order to generate avirtual-viewpoint image corresponding to a designated virtual viewpoint;obtaining an audio collection signal based on collection of audio of anaudio collection target region by a microphone, wherein the audiocollection target region includes at least a part of a capturing rangeof the plurality of cameras; and generating an audio signal to bereproduced together with the virtual-viewpoint image corresponding tothe specified capture time, by using the obtained audio collectionsignal, wherein the audio collection signal is based on collection bythe microphone at a point in time prior to the specified capture time.